Distillation of acid treated oils



Dec. 31, 1935. B. A

Y DISTILLATION OF ACID TREATED OILS Filed Aug. 4, 1933 ing the acid radical.

Patented Dec. 31, 1935 'ATN oFcE Brian Mead, Houston, Tex., assignor to Standard Oil Development flompany, a corporation of Delaware Application August 4, 1933, Serial No. 683,639

9 Claims.

This invention relates to a process of distilling .acid treated oils and will be fully understood from the following description when read in conjunction with the drawing, the sole figure of which is a diagrammatic side elevation partly in section of the apparatus used in carrying it out.

The invention may be used in conjunction with the distillation of various types of mineral oils such as naphthas, petroleum lubricating oils, shale oils, hydrogenated tars or coals, etc., which have been acid treated and which on distillation develop certain undesirable characteristics due to decomposition of compounds contain- Since the greatest advantages of the present process are obtained when it is applied to the redistillation of acid treated naphthas, and especially of acid treated cracked naphthas, the same will be described in more detail in conjunction with its last mentioned application.

Redistillation of a cracked naphtha which has been treated with sulphuric acid is the usual method employed for improving the color and lowering the gum and sulphur content of the stock, these changes being effected through removal of polymers. In the course of thisdistillation, S02 is often evolved through the thermal breakdown of sulphuric acid esters present in the acid treated charge. This gas passes out of the still in company withthe overhead products, the color of which is impaired by its presence. If, however, a small amount of caustic is added to the charge, the S02 is converted to sodium sulphite as rapidly as it is formed and the deleterious efiect of the gas on the overhead is thus eliminated. It has been found that the use of caustic in this manner has resulted in an 8 shade Saybolt color improvement in certain instances, the average improvement for a large number of naphthas being approximately shades.

In practice, it has been found advantageous to substitute for the caustic an oil-soluble soap such as the crude sodium naphthenate obtained as a by-product in distilling naphthene base oils over caustic. Corn oil soap, cocoanut oil soap, cotton seed oil soap may be mentioned as examples of other oil-soluble soaps giving good results.

The advantages possessed caustic are as follows:

(1) Since the material is oil-soluble, much better contact is obtained between the reagent and the S02.

(2) It has been found that excessive amounts by the soap over of caustic have a deleterious effect on the cop- I per dish gum and breakdown time of the overhead. When caustic-is fed to the distillation equipment it is difiicult to control its application within such limits that sufficient caustic is provided for reaction with the $02 on the one hand while an amount sufficient to adversely aifect the gum is not used on the other.

(3) Deposition of inorganic matter on the heating surface of the: still is much less in the case where naphthenic soaps are used than when caustic is used. I

Although a great number o-f'alkaline bodies such as caustic soda, -etc., capable of reacting with S02 may be used in our process, the use of oil-soluble soaps is especially contemplated in our-invention due to the above enumerated advantages.

Referring now to the figure, the apparatus will be briefly described in conjunction with the method of operating the same.

The acid treated oil from tank I and the oilsoluble soaps from tank 2 are passed by means of pumps 3 and 4 through meters 5 and 6 and line i into the re-run battery. The oil-soluble soap may be previously dissolved in a solvent such as a heavy lubricating oil. The rerun battery, in case of redistilling naphtha, may consist of tower 8 which is heated by means of a closed steam coil 9 at the bottom thereof. The tower is provided with the usual bell cap plates. All the unvaporized residue is removed through line I i into residue tank l2. Overhead distillate which leaves the tower through line is is condensed in condenser M which is connected with a source of vacuum by line l5. The condensed distillate is passed through line l6 by pump I! to the distillate tank i8. The line I 9 serves for the return of reflux condensate to the tower.

The following example will illustrate our process.

A sample of cracked naphtha is treatedwith 3 pounds per barrel of 98% sulfuric acid by agitation. The acid oil is allowed to settle, is separated from the sludge by decantation then water washed and neutralized with caustic soda. The neutralized oil is then filtered to remove'the excess caustic soda and divided into two portions.

distillates are again divided into two equal portions, the one portion being washed with a sodium carbonate solution and the other being doctor sweetened. The Saybolt colors on the sodium carbonate washed and on the doctor sweetened overheads from the two distillates are the following:

Another sample of cracked naphtha is treated with six pounds per barrel of 98% acid and then further treated in an analogous manner. The color inspections are the following:

Sample distilled in Sample distilled the absence of over naphthenic naphthenic soap soap Carbon- Doctor Carbon- Doctor ate sweeta sweet- Washed ened washed ened Color (Robinson) 22 23 27 27 Color after 16 hours exposure at 212 F 20 20 24 22 Sample distilled in absence of soap Sample dis tilled in presence of soap Mgms. so, per liter of overhead 67.0 1. 4

Reduction of the S02 content of the overhead distillate to the extent indicated by the above figures suggests another advantage in using the naphthenate soap products: corrosion of the plant rerun equipment is greatly reduced. Experimental data on plant rerun equipment show that the use of naphthenate soap diminishes the iron loss from 7.18 pounds per day to 0.78 pound per day which corresponds to an 89.2% reduction in corrosion.

. The present process may be varied in several ways; therefore, it is not to be limited by the above example but only by the following claims in which it is my intention to claim all novelty inherent in the invention.

What I claim is: i 1. The process of distilling an acid treated mineral oil which comprises adding a sufficient quantity of an oil-soluble soap to the oil to practically completely take up any acid-reacting substance evolved from any residue of the treating acid during the distillation of the oil and carrying out the distillation in the presence of said oil-soluble soap.

2. The process of distilling an acid treated mineral oil which comprises adding a sufficient quancity of an alkali naphthenate to the oil to practically completely take up any acid-reacting substance evolved from any residue of the treating acid during the distillation of the oil and carrying out the distillation in the presence of said alkali naphthenate.

3. The process of distilling an acid treated mineral oil which comprises adding a suflicient quantity of sodium naphthenate to the oil to practically completely take up any acid-reacting substance evolved from any residue of the treating acid during the distillation of the oil and carrying out the distillation in the presence of said sodium naphthenate.

4. The process of distilling an acid treated petroleum oil which comprises adding a sufiicient quantity of an oil-soluble soap to the oil to practically completely take up any acid-reacting substance evolved from any residue of the treating acid during the distillation of the oil and carrying out the distillation in the presence of said oilsoluble soap. I V

5. The process of distilling an acid treated petroleum oil which comprises adding a sufficient quantity of an alkali naphthenate to the oil to 2 practically completely take up any acid-reacting substance evolved from any residue of the treating acid during the distillation of the oil and carrying outthe distillation in the presence of said alkali naphthenate.

6. The process of distilling an acid treated petroleum oil which comprises adding a sumcient quantity of sodium naphthenate to the oil to practically completely take up any acid-reacting substance evolved from any residue of the treating acid during the distillation of the oil and carrying out the distillation in the presence of said sodium naphthenate.

7. The process of distilling an acid treated petroleum naphtha which comprises adding a sufiicient quantity of anioil-soluble soap to the naphtha to practically completely take up any acid-reacting substance evolved from any residue of the treating acid during the distillation of the naphtha and carrying out the distillation in the presence of said oil-soluble soap.

8. The process of distilling an acid treated petroleum naphtha which comprises adding a sufficient quantity of an alkali naphthenate to the naphtha to practically completely take up any acid-reacting substance evolved from any residue of the treating acid during the distillation of the naphtha and carrying out the distillation in the presence of said alkali naphthenate.

9. The process of distilling an acid treated petroleum naphtha which comprises adding a sufficient quantity of sodium naphthenate to the naphtha to practically completely take up any acid-reacting substance evolved from any residue of the treating acid during the distillation of the naphtha and carrying out the distillation in the presence of said sodium naphthenate.

BRIAN MEAD. 

